Planetary power take off device

ABSTRACT

A power take off device includes input and output shafts and an integral planetary gear set. The power take off device may be a single speed or a two speed device. The input shaft and the output shaft are mechanically connected through the planetary gear set. In one mode of operation of the power take off device, a substantial speed reduction and torque increase is provided between the input shaft and the output shaft. The power take off device may change to a second mode of operation without stopping to provide a direct one to one speed and torque ratio between the input shaft and the output shaft. A planetary gear set clutch unit includes a two direction actuator that provides fluid pressure actuation and release of the clutch unit with a single input signal.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date of U.S.Provisional Patent Application Ser. No. 61/105,859, filed Oct. 16, 2008,the disclosure of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to a power take off device that suppliespower from a power source to a driven accessory. More specifically, theinvention relates to a power take off device with an integral planetarygear set and at least one clutch that provides power at various outputspeeds to the driven accessory.

BACKGROUND OF THE INVENTION

Power take off devices are commonly used with power sources such asvehicle engines or motors or vehicle transmissions to provide power to adriven accessory. For example, power take off devices are commonly usedon farm tractors to provide power to accessories such as mowers or otheraccessories, on highway vehicles to provide power to accessories such aswinches or pumps or blowers, on industrial equipment to provide power topumps and blowers and other accessories, and on marine vehicles toprovide power to pumps and propulsion devices and other accessories.

A typical power take off device can include a housing, an input gearthat extends out of the housing, and an output shaft that also extendsout of the housing. When the power take off device is mounted to asource of rotational power, the input gear meshes with and is driven bya drive gear that is driven by the power source. The input gear isdirectly or indirectly drivingly connected to the output shaft withinthe housing to transmit power from the input shaft to the output shaft.An accessory is drivingly connected to the output shaft and in turn ispowered by the power source. The power take off device may provide aconstant speed ratio or a speed reduction or a speed increase betweenthe input gear and the output shaft and may include a clutch to engageand disengage the drive connection between the input gear and the outputshaft.

In certain uses of power take off devices, it would be advantageous toprovide two or more speed ratios rather than a single constant speedratio between the input gear and the output shaft. For example, when apower take off device is used to propel a blower, it would beadvantageous for the power take off device to provide a gear reductionthat provides relatively lower speed and relatively greater torque ofthe output shaft to overcome the relatively high inertia forces of theblower at start up. Once the blower has reached a particular rotationalspeed, it would be advantageous for the power take off device toincrease the speed of the output shaft and of the blower. This two ratioor two stage or two speed approach could reduce the stress on a clutchwithin the power take off device during such start up of the blower.Another application in which it would be advantageous for the power takeoff device to rotate the output shaft first at a slower speed and thenat a faster speed is when the power take off device is used to power awinch. In this application, it would be advantageous to rotate the winchat a greater speed when the winch cable is being played out to reach aload and to then rotate the winch at a slower speed with increasedtorque to retrieve the load.

It would also be advantageous in certain uses of power take off devicesto provide a large speed reduction gear ratio between the input gear andthe output shaft while achieving a small compact size. For example, inmany uses of power take off units on vehicle transmissions, the spaceavailable for the power take off unit is limited, yet it can bedesirable to provide a large speed reduction gear ratio that provides acorrespondingly large torque increase. In conventional power take offunits it can be difficult to achieve a large speed reduction gear ratiowhile achieving a compact size. This is because a large speed reductiongear ratio can require at least one relatively large diameter gear thathas a longitudinal axis laterally offset relative to the axis of a smallgear that drives the large gear.

As used herein, a power take off device means a mechanical ormechanical—fluid device that transmits power directly or indirectly froma power source to a driven accessory. A removable power take off deviceis a power take off device that has releasable fasteners that removablyconnect the device to the power source. A transmission mounted powertake off device is a power take off device that is mounted to atransmission that transmits power from a primary power source such as amotor or engine of a vehicle to a primary powered device such as thepropulsion component of the vehicle, in a manner such that the powertake off device transmits power from the primary power source throughthe transmission to the driven accessory independently of transmissionof power to the primary powered device.

SUMMARY OF THE INVENTION

The present invention provides a power take off device, a removablepower take off device, and a transmission mounted or transmissionmounted removable power take off device that can provide single speedoperation, two speed operation, or three or more speed operation. Theinvention provides such a power take off device in which an input gear,an output device and a planetary gear set that includes a sun gear, acarrier with associated planet gears, and a ring gear are all providedin an integral unitary structure.

The invention also provides such a device that includes one or moreclutches and can change the speed ratio without stopping the rotationalmovement of the input gear or of the output device. The invention in oneembodiment provides a two speed output capability that may for examplehave a direct drive 1:1 ratio and a speed reduction or speed increaser.The invention in another embodiment provides a single speed output thathas an extended range of reduction ratios or speed increase ratios. Theinvention provides a compact power take off unit in which the inputshaft and output shaft and planetary gear set have the same longitudinalaxis, to decrease the lateral size requirements of the power take offdevice. The planetary gear set in conjunction with a cluster gear set atthe input of the power take off unit provides a wide choice of outputspeed and torque ranges, so that the power take off device can be usedin a wide variety of different applications with different requirementsby changing just a few components. The invention also provides aclutch/brake unit actuator that provides fluid pressure actuation andfluid pressure release of the unit with a single control signal.Further, the invention provides various ones of the features andstructures described in the claims set out below, alone and incombination, which claims are incorporated by reference in this summaryof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this invention will now be described in further detailwith reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional side elevation view of apresently preferred embodiment of a power take off device incorporatingcertain principles of this invention, in which a two speed power takeoff device is provided;

FIG. 2 is a perspective view of the power take off device shown in FIG.1;

FIG. 3 is a longitudinal cross-sectional side elevation view of analternative embodiment of a power take off device incorporating certainprinciples of this invention, in which a two speed power take off deviceis provided;

FIG. 4 is a longitudinal cross-sectional side elevation view of anotheralternative embodiment of a power take off device incorporating certainprinciples of this invention, in which a single speed power take offdevice is provided; and

FIG. 5 is a longitudinal cross-sectional side elevation view of twoother alternative embodiments of a power take off device incorporatingcertain principles of this invention, in which a single speed power takeoff device is provided.

DETAILED DESCRIPTION OF THE INVENTION

The principles, embodiments and operation of the present invention areshown in the accompanying drawings and described in detail herein. Thesedrawings and this description are not to be construed as being limitedto the particular illustrative forms of the invention disclosed. It willthus become apparent to those skilled in the art that variousmodifications of the embodiments herein can be made without departingfrom the spirit or scope of the invention.

A preferred embodiment of the present invention is shown in FIGS. 1 and2. A power take off device 10 includes an input drive 11, an inputhousing 12, an output drive 13, an output housing 14, an end cap 15, aplanetary gear set 16, planetary gear set wet clutch/brake units 17 and18, and a planetary housing 19. A pump 20 provides a source of fluidpressure for lubricating the power take off device 10 and forcontrolling the operation of the power take off device 10. The housings12, 14 and 19 and the end cap 15 are separate components, but some maybe integral with one another and together they provide a unitary housing21 for the power take off device 10 that has a unitary outer surface anda unitary inner surface with the inner surface defining a unitarycentral opening or cavity. As used herein, unitary means integral, orseparate but connected together without relative movement, and providinga functional single structure

In the preferred embodiment, the power take off device 10 is removablymounted by bolts to a transmission of an internal combustion enginepowered over the highway truck to drive a blower that is mounted on thetruck to pull leaves and other debris from a street into a containermounted on the truck. The engine of the truck also powers the pump 20.The over the highway truck, engine, transmission, mounting bolts, blowerand container are further described below and are not illustrated in thedrawings. Alternatively, the power take off device 10 may be adapted formounting to a motor or engine or other prime mover or to a transmissionof a truck or tractor or industrial vehicle or marine vehicle orstationary unit or other rotational power source.

The input housing 12 includes a central opening 24 (FIG. 1) and boltholes 25 (FIG. 2) that receive the bolts for securing the power take offdevice 10 to the transmission mentioned above of the over the highwaytruck on which the power take off device 10 is used. The input drive 12includes an input cluster gear 26 that is partially disposed in thecentral opening 24. The cluster gear 26 includes a larger diameter gear27 and a smaller diameter gear 28 mounted on an idler shaft (not shown)that extends between idler shaft support bushings 29 and 30 in the inputhousing 12.

The cluster gear 26 can be removed from the input housing 12, and thesmaller diameter gear 28 can removed from the larger diameter gear 27,to change the input gear ratios of the power take off device 10 in awell known manner. The input gear cluster 26, and particularly the inputgear 27, extends laterally out of the input housing 12 and meshes with adrive gear (not shown) of the transmission of the over the highway truckto which the power take off unit 10 is removably attached. In thismanner, rotational torque and power from the engine of the truck istransmitted to the power take off device 10 through the trucktransmission independently of the speed and direction of travel of thetruck. The input drive 11 also includes a transfer gear 35 that is fixedto and transfers torque and power to an input shaft 36 from the gear 27.The input shaft 36 is rotatably journaled at its right end in a bearingin the end cap 15.

The output drive 13 includes an output shaft 37 that is rotatablyjournaled in the output housing 14. The left end of the output shaft 37is connected to rotatably drive the above described blower. The outputshaft 37 also includes a blind bore 38 that includes a bushing intowhich the left end of the input shaft 36 is rotatably journaled. Alongitudinal passage 39 in the input shaft 36 receives fluid from thepump 20 through the line 40 and fitting 41 (FIG. 2), and a reduceddiameter orifice 42 at the left end of the passage 39 provides fluid tolubricate the bushing in the blind hole 38.

The end cap 15 includes a blind hole that carries a bearing forsupporting the right end of the input shaft 36. The end cap 15 alsoincludes a threaded port on its exterior surface that receives the fluidfitting 41 and an opening 43 for on its exterior surface that receives asolenoid valve 44. The solenoid valve 44 is shown in FIG. 2 but isremoved in FIG. 1 for clarity. The solenoid valve 44 is a well knowndevice and includes an electrical solenoid (not shown) that is poweredby an electrical signal to open and close fluid communication betweenthe fitting 41 and a fitting 45.

The planetary gear set 16 includes a sun gear 51, a planet gear set 52,and a ring gear 53. The sun gear 51 has a pitch diameter S. The sun gear51 is carried on and fixed to the left end of the input shaft 36, sothat the sun gear 51 is driven by and rotates with the input shaft 36.The planet gear set 52 includes a planet carrier 54 that is integrallyformed on the output shaft 37, so that the output shaft 36 rotates withthe planet carrier 54. The planet carrier 54 carries four individualplanet gears 55, each of which is rotatably journaled on the planetcarrier 54 and two of which are shown in FIG. 1. Each planet gear 55meshes with both the sun gear 51 and the ring gear 52, in a well knownmanner. The ring gear 53 has a pitch diameter R and is fixed to androtates with a ring gear hub 56. The ring gear hub 56 is rotatablyjournaled in a ring gear bushing 57 in the planetary housing 19, so thatthe ring gear 53 and ring gear hub 56 are rotatably disposed in thehousing 19.

The planetary gear set wet clutch/brake unit 17 includes a first set ofgenerally flat laterally extending plates 62 each fixed to and carriedby the planetary housing 19 and a second set of similar generally flatlaterally extending plates 63 disposed between adjacent ones of theplates 62 and each fixed to and carried by the ring gear hub 56. Whenthe unit 17 is released, the first set of plates 62 and the second setof plates 63 are free to rotate with respect to one another. Thispermits relative rotational movement between the housing 19 and the ringgear hub 56 and ring gear 53. When the unit 17 is actuated, the firstset of plates 62 and the second set of plates 63 engage one another andpreclude relative rotational movement between the housing 19 and thering gear hub 56 and ring gear 53. A conventional multi-plate wetclutch/brake unit 17 is shown and described, but alternatively any othertype of clutch/brake unit can be used in place of the multi-plate unitsdescribed above and below herein. For example, a band type clutch/brakeunit might be used that includes a band that can be tightened about arotating member and an actuator. The term clutch or clutch unit hereinrefers to any device that moves between one position that permitsrelative rotational movement and another position that limits orprecludes relative rotational movement between first and second members,whether such members are stationary or rotatable. The term brake orbrake unit herein refers to any device that moves between one positionthat permits relative rotational movement and another position thatlimits or precludes relative rotational movement between first andsecond members, wherein one such member is rotatable and the other suchmember is stationary.

The planetary gear set wet clutch unit 18 includes a first set ofgenerally flat laterally extending plates 64 each fixed to and carriedby the input shaft 36 and a second set of similar generally flatlaterally extending plates 65 disposed between adjacent ones of theplates 64 and each fixed to and carried by the ring gear hub 56. Whenthe unit 18 is released, the first set of plates 62 and the second setof plates 63 are free to rotate with respect to one another. Thispermits relative rotational movement between the input shaft 36 and thering gear hub 56 and ring gear 53. When the unit 18 is actuated, thefirst set of plates 64 and the second set of plates 65 engage oneanother and preclude relative rotational movement between the inputshaft 36 and the ring gear hub 56 and ring gear 53.

Actuation and release of the clutch unit 18 is controlled by fluidpressure in the longitudinal passage 39. The pressure in the passage 39is communicated to the end face of the actuator piston 71 by a lateralpassage in the input shaft 36. When fluid pressure from the pump 20through line 40 and fitting 41 is communicated to the longitudinalpassage 39 and actuator piston 71, the unit 18 is engaged. When thisfluid pressure is isolated from the passage 39 and actuator piston 71,the unit 18 is released in a well known manner.

Actuation and release of the clutch unit 17 is controlled by a two areaactuator 73 that provides fluid pressure actuation and fluid pressurerelease of the unit 17 with a single control signal. The actuator 73 hasa relatively large annular lateral cross sectional area A1 exposed tocontrol fluid pressure from the pump 20 through the fitting 45. Thecontrol fluid pressure to the fitting 45 is controlled by the solenoidvalve 44. The annular lateral cross sectional area A1 is the differencebetween the lateral cross sectional area of a first machined bore 74 inthe central opening 24 in the input housing 12 in which a first portionof the actuator 73 is slidably and sealingly received and a secondlarger diameter stepped machined bore 75 in the opening 24 in which alarger diameter portion of the actuator 73 is slidably and sealinglyreceived. The actuator 73 also includes a stationary spacer 76 that issecured between a third larger diameter stepped machined bore 77 in thecentral opening 24 of the input housing 12 and the planetary housing 19.The actuator 73 is slidably and sealingly received in the insidediameter of the stationary spacer 76, and the actuator 73 has a lateralcross sectional area exposed to fluid pressure from the pump 40 througha fitting 78. The lateral cross sectional area A1 of the actuator 73that is intermittently exposed to control fluid pressure from thesolenoid valve 44 is significantly larger than the lateral crosssectional area of the actuator 73 that is constantly exposed tosubstantially the same fluid pressure from the pump 20 through thefitting 78. When the fluid control signal from the solenoid 44 isprovided to the area A1, the actuator 73 is pushed to the left andactuates the unit 17 to stop rotational movement of the ring gear hub 56and ring gear 57 relative to the housing 19. When the fluid controlsignal from the solenoid 44 is released and the pressure acting againstarea A1 is reduced, the actuator 73 is pushed to the right by the fluidpressure from the pump 20 through the fitting 78. In this manner, theactuator 73 is moved in opposite directions to actuate and release theunit 17 using only a single control signal.

Referring still to FIGS. 1 and 2, the mechanical input received by theinput gear 28 is transmitted through the planetary gear set 16 to theoutput shaft 37. When the unit 17 is released and the unit 18 isactuated, the sun gear 51 and the ring gear 53 are linked together. Thisprovides a 1:1 ratio of relative movement between the input shaft 36 andthe output shaft 37. When the unit 17 is actuated and the unit 18 isreleased, the ring gear 53 is stationary. This provides a gear ratio of1+R/S, which produces a substantial speed reduction and torque increase.When both units 17 and 18 are released, the power take off unit is in aneutral mode and torque and power from the input shaft 36 is nottransmitted to the output shaft 37. When both units 17 and 18 areactuated, the power take off unit is locked against rotational movementof either the input shaft 36 or the output shaft 37.

When the power take off unit 10 is mounted on an over the highway trucktransmission and used to drive a large blower (or fan), the gear of thetransmission that meshes with the input gear 28 of the power take offunit 10 rotates the input shaft 36. With both units 17 and 18disengaged, the power take off unit is in neutral and the blower is notdriven. When the unit 17 is actuated and the unit 18 remains released,the ring gear hub 56 and ring gear 53 are grounded to the housing 19. Inthis mode, the input shaft 36 drives the sun gear 38 and the planetcarrier 54 rotates the output shaft 37. This provides the rotationalspeed reduction ratio of 1+R/S for the output shaft 37 relative to theinput shaft 36, to overcome the inertial forces of the blower at startup. When the blower has reached sufficient speed with this ratio, thepower take off unit 10 is changed to a second speed ratio. The unit 17is released and the unit 18 is actuated. In this mode, the sun gear 51and the ring gear 53 are linked together resulting in a 1:1 ratio ofrelative rotational movement between the input shaft 36 and the outputshaft 37. This provides a relatively faster speed than the first mode todrive the blower at its appropriate operating speed.

With this structure, the input drive 11 and planetary drive 16 andoutput drive 13 are all arranged along a single longitudinal axis toreduce bulk and provide a compact power take off unit with multiplespeed ratios. Further the clutch units 17 and 18 are coaxially arrangedin a nested relationship (one laterally disposed inside the other, insubstantial laterally aligned relationship) in which both units provideengagement and disengagement of the ring gear relative to other elementsof the power take off unit 10.

Referring now to FIG. 3, a second embodiment of a two speed planetarypower take off device 110 is shown. The power take off device 110 isillustrated as having a single input gear 112 that is driven by atransmission. Those skilled in the art will recognize that additionalgears, i.e., cluster gears as shown if FIGS. 1 and 2, may be used forinputting power into the power take off device 110. In FIG. 3, the inputgear 112 has a portion that forms the sun gear of the planetary gearset, hereinafter, the sun gear 114. The input gear 112 also includes anannular portion 116 for supporting clutch plates 118.

The planetary gear set also includes a carrier 126 for supporting planetgears 128 and a ring gear 130. The carrier 126 is fixedly attached to,or alternatively is integral to, the output shaft 134 of the power takeoff device 110. A plurality of clutch plates 136 is attached to theoutput shaft 134 in a location associated with clutch plates 118. Clutchplates 118 and 136 for portions of a wet clutch 140 that is actuated bymovement of a clutch piston 142 in a clutch cylinder 144. Fluid pressurepassing through passages in the output shaft 134 causes movement of thepiston 142 toward the clutch disks 118 and 136 to engage the clutch 140.Generally, a resilient member, such as a spring, is used to disengagethe clutch 140 when the fluid pressure acting on the piston 142 isreduced below a predetermined amount.

The power take off device 110 of FIG. 3 is a two speed (two ratio) powertake off device. Although described as providing a reduction function,the gearing could alternatively provide an overdrive function dependingupon which portion of the planetary gear set is grounded. Duringoperation of the device 110, if clutch 140 is engaged and brake 148 isdisengaged, the device 110 provides a 1:1 ratio and the input gear 112directly drives the output shaft 134 through the clutch 140. If,however, clutch 140 is disengaged and brake 148 is engaged, the powertake off device 110 provides a reduction equal to 1+R/S (where R is thepitch diameter of the ring gear 130 and S is the pitch diameter of thesun gear 114) through the planetary gear set with sun gear 114 drivingthe carrier 126 and the ring gear 130 being grounded.

FIG. 4 illustrates another embodiment of a planetary power take offdevice 210 according to certain features of the present invention. Thepower take off device 210 is a single speed planetary power take offdevice in which a coaxial input shaft, output shaft and planetary gearset provide a speed increase and a corresponding torque decrease in acompact size. The single speed power take off device 210 shown in FIG. 4is similar in many respects to the two speed power take off device 10shown in FIGS. 1 and 2 and described above, except that (a) the singlespeed power take off device 210 has only one clutch/brake unit asdescribed below while the two speed power take off device 10 has twoclutch/brake units, and (b) the single speed power take off device 210provides a speed increase (overdrive) gear ratio as opposed to the 1:1direct drive ratio and the speed reduction ratio provided by the twospeed power take off device 10. The power take off device 210 couldalternatively be arranged to provide a speed reduction and torqueincrease function, by arranging the stationary and rotating gears of theplanetary gear set in a manner similar to that shown in FIGS. 1 and 2.Component parts of the power take off device 210 and circuit that arestructurally and/or functionally similar to component parts describedabove with reference to FIGS. 1 and 2 are identified below by the samereference number as used in describing FIGS. 1 and 2 above, with theaddition of a prefix “2.” For brevity, the description above pertainingto these component parts and circuit of FIGS. 1 and 2 is not fullyrepeated below, but such description above applies to FIG. 4 unlessotherwise mentioned below or otherwise illustrated in FIG. 4.

In the embodiment shown in FIG. 4, the power take off device 210 is alsoremovably mounted by bolts to a transmission of an internal combustionengine powered over the highway truck. The engine of the truck alsopowers a pump 220, and the device 210 is preferably mounted in a circuitsimilar to that shown in FIG. 2 and described above. Alternatively, thepower take off device 210 may be adapted for mounting to a motor orengine or other prime mover or to a transmission of a truck or tractoror industrial vehicle or marine vehicle or stationary unit or otherrotational power source.

Referring still to FIG. 4, the power take off device 210 includes aninput drive 211, an input housing 212, an output drive 213, an outputhousing 214, a planetary gear set 222, a planetary gear set wetclutch/brake unit 217, and a planetary housing 219. The input housing212 includes a central opening 224 and bolt holes (not shown) thatreceive bolts for securing the power take off device 210 to thetransmission mentioned above of the over the highway truck on which thepower take off device 10 is used. The input drive 212 includes an inputcluster gear 226 that is partially disposed in the central opening 24.The cluster gear 26 includes a larger diameter gear 227 and a smallerdiameter gear 228 mounted on an idler shaft 231. The input drive 211also includes a transfer gear 235 that is fixed to and transfers torqueand power to an input shaft 236 from the gear 227. The input shaft 36 isrotatably journaled at its right end in a bearing in the end cap 15.

The output drive 213 includes an output shaft 237 that is rotatablyjournaled in the output housing 214. The left end of the output shaft237 is connected to rotatably drive the above described blower.

A solenoid valve 244 is a well known device and includes an electricalsolenoid (not shown) that is powered by an electrical signal to open andclose fluid communication from the line 240.

The planetary gear set 222 includes a sun gear 245, a planet gear set246, and a ring gear 247. The sun gear 245 has a pitch diameter S. Thesun gear 245 is carried on and fixed to the right end of the outputshaft 237, so that the sun gear 245 drives and rotates with the outputshaft 237. The planet gear set 246 includes a planet carrier 248 that isintegrally formed on the input shaft 236, so that the input shaft 236drives and rotates with the planet carrier 248. The planet carrier 248carries four individual planet gears 249, each of which is rotatablyjournaled on the planet carrier 248 and two of which are shown in FIG.4. Each planet gear 55 meshes with both the sun gear 245 and the ringgear 247, in a well known manner. The ring gear 247 has a pitch diameterR and is fixed to and rotates with a ring gear hub 250. The ring gearhub 250 is rotatably journaled in a ring gear bushing in the planetaryhousing 219, so that the ring gear 247 and ring gear hub 250 arerotatably disposed in the housing 219.

The planetary gear set wet clutch/brake unit 217 includes a first set ofgenerally flat laterally extending plates 262 each fixed to and carriedby the planetary housing 219 and a second set of similar generally flatlaterally extending plates 263 disposed between adjacent ones of theplates 262 and each fixed to and carried by the ring gear hub 250. Whenthe unit 217 is released, the first set of plates 262 and the second setof plates 263 are free to rotate with respect to one another. Thispermits relative rotational movement between the housing 219 and thering gear hub 250 and ring gear 247 to provide a neutral mode. When theunit 217 is actuated, the first set of plates 262 and the second set ofplates 263 engage one another and preclude relative rotational movementbetween the housing 219 and the ring gear hub 250 and ring gear 247. Inthis mode, the ring gear 247 is grounded while the planet carrier 248rotates with the input shaft 236, to provide an increased speed of theoutput shaft 237 relative to the input shaft 236 at a speed ratio equalto 1/(1+S/R).

Actuation and release of the clutch unit 217 is controlled by a two areaactuator 273 that provides fluid pressure actuation and fluid pressurerelease of the unit 217 with a single control signal. The actuator 273has a relatively large annular lateral cross sectional area exposed tocontrol fluid pressure from the pump 220 controlled by the solenoidvalve 244. The annular lateral cross sectional area is the differencebetween the lateral cross sectional area of a first machined bore 274 inthe central opening 224 in the input housing 212 in which a firstportion of the actuator 273 is slidably and sealingly received and asecond larger diameter stepped machined bore 275 in the opening 224 inwhich a larger diameter portion of the actuator 273 is slidably andsealingly received. The actuator 273 also includes a stationary spacer276 that is secured between a third larger diameter stepped machinedbore 277 in the central opening 224 of the input housing 212 and theplanetary housing 219. The actuator 273 is slidably and sealinglyreceived in the inside diameter of the stationary spacer 276, and theactuator 273 has a lateral cross sectional area exposed to fluidpressure from the pump 40. The lateral cross sectional area of theactuator 273 that is intermittently exposed to control fluid pressurefrom the solenoid valve 244 is significantly larger than the lateralcross sectional area of the actuator 273 that is constantly exposed tosubstantially the same fluid pressure from the pump 220. The actuator273 operates in a similar manner to the operation of the actuator 73described above with reference to FIGS. 1 and 2.

FIG. 5 illustrates two additional embodiments of power take off devices310 and 410 according to the present invention. For ease ofunderstanding, power take off devices 310 and 410 are both illustratedin FIG. 5 and are separated from one another by the central axis of theoutput shaft 394.

The power take off device 310 shown in the upper half of FIG. 5 includesa clutch 382, similar to that described above with regard to clutch 140.When engaged, clutch 382 connects the ring gear 384 of the planetarygear set to the input gear 386. The carrier 388 for the planet gears 390is fixed for rotation with the output shaft 394, while the sun gear 392is grounded (or fixed relative to the housing of the power take offdevice 310). The power take off device 310 is a single speed (singleratio) power take off device. When clutch 382 is engaged, the input gear386 drives the ring gear 384, which, in turn, drives the carrier 388 forcausing rotation of the output shaft 394. This design provides a mediumreduction.

The power take off device 410 shown in the lower half of FIG. 5 includesa clutch 402 that is similar to clutch 140. When engaged, clutch 402connects the sun gear 404 of the planetary gear set to the input gear406. The carrier 408 for the planet gears 409 is fixed for rotation withthe output shaft 494, while the ring gear 412 is grounded (or fixedrelative to the housing of the power take off device 410). Power takeoff device 410 is a single speed power take off device. When clutch 402is engaged, the input gear 406 drives the sun gear 404, which, in turn,drives the carrier 408 for causing rotation of the output shaft 494.This design provides a deeper reduction (equal to 1+R/S) relative tothat shown in the upper half of FIG. 5, where R is the pitch diameter ofthe ring gear 412 and S is the pitch diameter of the sun gear 404.

The power take off devices 10, 110, 210, 310 and 410 may each bemodified to provide various input shaft to output shaft speed and torqueratios and/or to provide a clutch function through their respectiveplanetary gear sets in various arrangements. For example, a clutch maybe used between and among other ones of the rotating parts to facilitatestarting and stopping the output shaft while the input shaft continuesto rotate. Also, a clutch may be used between and among the housings,sun gears, planet carriers and ring gears to provide various speed andtorque ratios. If any two of the sun gears, planet carriers and ringgears of any of the planetary gear sets of any of the power take offdevices 10, 110, 210, 310 and 410 are locked together (permanently orthrough a clutch) while the other is not locked, the respectiveplanetary gear set will provide a 1:1 speed ration between the inputshaft and the output shaft. Also, if the input shaft of any planetarygear set is locked to the sun gear (with pitch diameter S) and theoutput shaft is locked to the planet carrier while the ring gear (withpitch diameter R) is stationary in any of the embodiments, the speedratio will be a reduction of 1+R/S (as in the embodiments shown in FIGS.1 and 2, 3 and the lower half of FIG. 5). If the input shaft is lockedto the planet carrier and the output shaft is locked to the ring gearwhile the sun gear is stationary, the speed ratio will be a speedincrease of 1/(1+S/R). If the input shaft is locked to the sun gearwhile the output shaft is locked to the ring gear and the planet carrieris stationary, the speed ration will be a reduction with the outputdirection reversed of −R/S. The various embodiments of the inventionshown and described above, with or without any of these modifications orchanges, provides a compact, universal, integral planetary power takeoff device with relatively small lateral dimensions that will provide awide variety of large and small speed and torque ratios with a minimumnumber of parts.

Presently preferred embodiments of the invention are shown and describedin detail above. The invention is not, however, limited to thesespecific embodiments. Various changes and modifications can be made tothis invention without departing from its teachings, and the scope ofthis invention is defined by the claims set out below.

1. A power take off device comprising: a housing; an input gear; anoutput shaft; a planetary gear set within the housing, the planetarygear set including a sun gear, a ring gear, and a carrier supportingplanet gears, one of the sun gear, the ring gear and the carrier beinggrounded relative to the housing, a second one of the sun gear, the ringgear and the carrier being grounded relative to the housing, a third oneof the sun gear, the ring gear, and the carrier being driven by theinput gear, and the output shaft being connected to the driven one ofthe sun gear, the ring gear and the carrier.
 2. The power take offdevice set forth in claim 1, wherein the power take off device is asingle speed device.
 3. The power take off device set forth in claim 1,wherein the power take off device is a two speed device, a clutch beingused to transition between a first gear ratio and a second gear ratio.4. A power take off device comprising: a housing, said housing having anouter surface and an inner surface, said inner surface defining acentral cavity, and a plurality of openings extending from said outersurface to said inner surface to provide access to said central cavity,an input gear, said input gear being disposed in one of said openings,at least a portion of said input gear being disposed within said centralcavity, and at least a portion of said input gear being disposed outsidesaid central cavity outwardly of said outer surface, an output device,said output device being disposed in another one of said openings, andat least a portion of said output device being disposed outside saidcentral cavity outwardly of said outer surface, and an intermediate gearset disposed entirely within said central cavity and mechanicallyconnecting said input gear and said output device, said intermediategear set including a planetary gear set, said planetary gear setincluding a sun gear, a plurality of planet gears carried by a planetcarrier, and a ring gear; a first mechanical link connecting a first oneof sun gear and said planet carrier and said ring gear with said inputgear, a second mechanical link connecting a second one of said sun gearand said planet carrier and ring gear to said housing, and a thirdmechanical link connecting a third one of said sun gear and said planetcarrier and said ring gear to said output device.
 5. A power take offdevice as set forth in claim 4, wherein said first or third mechanicallink is a clutch having first and second clutch surfaces and a movableactuator arranged to move said clutch surfaces between an engagedposition and a disengaged position.
 6. A power take off device as setforth in claim 4, wherein said second mechanical link is permanentlygrounded to said housing and to said second one.
 7. A power take offdevice as set forth in claim 4, wherein the power take off device is asingle speed device.
 8. A power take off device as set forth in claim 4,including an input shaft driven by said input gear, said output deviceincluding an output shaft, said input shaft and said output shaft andsaid planetary gear set each having a longitudinal axis, and saidlongitudinal axes each being coaxial with one another.
 9. A power takeoff device as set forth in claim 8, wherein at least one of saidmechanical links is a clutch having first and second clutch surfaces anda movable actuator arranged to move said clutch surfaces between anengaged position and a disengaged position.
 10. A power take off deviceas set forth in claim 9, wherein said housing and said outer surface andsaid central opening are each unitary.
 11. A power take off device asset forth in claim 10, wherein said first or third mechanical link is aclutch having first and second clutch surfaces and a movable actuatorarranged to move said clutch surfaces between an engaged position and adisengaged position.
 12. A power take off device as set forth in claim4, wherein the power take off device is a two speed device
 13. A powertake off device as set forth in claim 12, including a first clutch and asecond clutch, said first mechanical link includes one of said clutches,and each of said clutches includes a movable actuator arranged to movesaid clutch between an engaged position and a disengaged position.
 14. Apower take off device as set forth in claim 13, wherein each of saidclutches includes a longitudinal axis, said axes are coaxial, and one ofsaid clutches is disposed laterally inwardly of and is substantiallylaterally aligned with the other of said clutches.
 15. A power take offdevice as set forth in claim 14, including an input shaft driven by saidinput gear, said output device including an output shaft, said inputshaft and said output shaft and said planetary gear set each having alongitudinal axis, and said longitudinal axes all being coaxial.
 16. Apower take off device as set forth in claim 15, wherein one of saidclutches acts between said ring gear and said housing, and the other ofsaid clutches acts between said ring gear and another rotatable elementwithin said housing.
 17. A power take off device as set forth in claim16, wherein said housing and said outer surface and said central openingare each unitary.
 18. A power take off device as set forth in claim 5,wherein said actuator is slidably disposed in said housing, saidactuator includes a first sealed annular cross sectional area facing inone longitudinal direction and a second sealed annular cross sectionalarea facing in a second longitudinal direction opposite said firstdirection, and said second area being substantially smaller than saidfirst area.
 19. A system comprising: a prime mover power source; aprimary powered device; a transmission including at least onetransmission gear and mechanically connecting said prime mover powersource and said primary powered device to transmit rotational torquefrom said prime mover power source to said primary powered device; anaccessory device; and a transmission mounted power take off device; saidpower take off device including; a unitary housing, said housing havinga unitary outer surface and a unitary inner surface, said inner surfacedefining a unitary central cavity, and a plurality of openings extendingfrom said outer surface to said inner surface to provide access to saidcentral cavity; an input gear, said input gear being disposed in one ofsaid openings, at least a portion of said input gear being disposedwithin said central cavity, and at least a portion of said input gearbeing disposed outside said central cavity outwardly of said outersurface and engaging said transmission gear; an output device, saidoutput device being disposed in another one of said openings, and atleast a portion of said output device being disposed outside saidcentral cavity outwardly of said outer surface and mechanicallyconnected to said accessory device; and an intermediate gear setdisposed entirely within said central cavity and mechanically connectingsaid input gear and said output device, said intermediate gear setincluding a planetary gear set; said planetary gear set including a sungear, a plurality of planet gears carried by a planet carrier, and aring gear; a first mechanical link connecting a first one of sun gearand said planet carrier and said ring gear with said input gear, asecond mechanical link connecting a second one of said sun gear and saidplanet carrier and ring gear to said housing, and a third mechanicallink connecting a third one of said sun gear and said planet carrier andsaid ring gear to said output device; an input shaft and an output shafteach having a longitudinal axis; said planetary gear set having alongitudinal axis; and said longitudinal axes being coaxial.
 20. Asystem as set forth in claim 19, including at least two clutches, saidclutches each having a longitudinal axis, said longitudinal axes of saidclutches being coaxial with said other longitudinal axes, one of saidclutches being nested within the other of said clutches, and saidclutches being substantially laterally aligned with one another.
 21. Atwo directional fluid pressure operated actuator including: a housing; afirst bore in said housing; a second bore in said housing coaxial withsaid first bore and having a smaller diameter than said first bore; afirst fluid passage in said housing in fluid communication with saidfirst bore; a second fluid passage in said housing in fluidcommunication with both said first bore and said second bore; a annularpiston; said piston having a first cylindrical surface slidably andsealingly received in said first bore between said first passage andsaid second passage and a second cylindrical surface slidably andsealingly received in said second bore; said piston having a firstannular lateral cross sectional area disposed between said first andsecond bores and in fluid communication with said second passage andfacing in one longitudinal direction; said piston having a secondannular lateral cross sectional area disposed between said first boreand another bore and in fluid communication with said first passage andfacing in a longitudinal direction opposite said one direction; and saidfirst area being substantially larger than said second area.
 22. Anactuator as set forth in claim 21, wherein: said housing includes athird bore coaxial with said first and second bores; said third bore isof larger diameter than said first bore; a spacer includes a largerdiameter outer portion slidably and sealingly disposed in said thirdbore; and said spacer includes a smaller diameter inner portion definingsaid other bore.
 23. An actuator as set forth in claim 22, including: afluid pressure source; said second passage being in open fluid pressurecommunication with said fluid pressure source; and said first passagebeing in on and off controlled fluid pressure communication with saidfluid pressure source.
 24. An actuator comprising: a housing; a firstbore in said housing; a second bore in said housing coaxial with saidfirst bore and having a smaller diameter than said first bore; a firstfluid passage in said housing in fluid communication with said firstbore; a second fluid passage in said housing in fluid communication withboth said first bore and said second bore; a annular piston; said pistonhaving a first cylindrical surface slidably and sealingly received insaid first bore between said first passage and said second passage and asecond cylindrical surface slidably and sealingly received in saidsecond bore; said piston having a first annular cross sectional areadisposed between said first and second bores and in fluid communicationwith said first passage and facing in a first longitudinal direction;said piston having a second annular cross sectional area disposedbetween said first bore and another bore and in fluid communication withsaid second passage and facing in a second longitudinal directionopposite said first direction; and said first area being substantiallylarger than said second area.
 25. An actuator as set forth in claim 24,including: a fluid pressure source; said second passage being in openfluid pressure communication with said fluid pressure source; and saidfirst passage being in on and off controlled fluid pressurecommunication with said fluid pressure source.